GetArtistEventsRx.kt

// Somewhere on the UI thread
class MyActivity : Activity {
  val repo: ArtistRepository
  //...
  
  fun getData() {
    showProgress()
    disposable = repo.fetchEvents(artist)
      .subscribe { 
        hideProgress
        showData(it)
      }
  }
  
  override fun onDestroy() {
    super.onDestroy()
    disposable.dispose()
  }
  
}


class ArtistRepository {
  //...
  
  fun fetchEvents(artist: Artist) : Observable {
    // Image the same RepositoryUtil in rx style
    return RepositoryUtil.isCacheStaleObservable(sharedPreferences, "ArtistEvent", artist.name, TimeUnit.HOURS.toSeconds(1))
      .flatMap { isStale -> 
         // Check if data has been stored over an hour ago from now
          if (isStale) {
              // Reset the cache time to "now"
              RepositoryUtil.resetCache(sharedPreferences, "ArtistEvent", artist.name)
              // Call webservice synchronously
              val freshEvents =  api.findArtistEvents(artist.name).execute().body()
              // Update/Insert events in database 
              bandsInTownDatabase.artistEventDao().upsert(freshEvents)
          }
                
          return database.artistEventDao().getEventsByArtistId(artist.id)
        }
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
    
  }
}

// Retrofit web service interface
interface BandsInTownApi {
    @GET("/artists/{artistName}/events")
    fun findArtistEvents(
        @Path("artistName") artistName: String
    ): Observable<List<ArtistEventResponse>>
}